Method of and apparatus for determining the shives content in a fiber suspension



Dec. 26, 1967 G. VON ALFTHAN 3,359,736

METHOD OF AND APPARATUS FOR DETERMINING THE SHI-VES CONTENT IN A FIBERSUSPENSION Filed April 6, 1965 iii 33: 5:5 5:5

INVENTOR GEOPG voN ALFTHAN BY ATTORNEY United States Patent 3,359,786METHOD OF AND APPARATUS FOR DETERMIN- ING THE SHIVES CONTENT IN A FIBERSUS- PENSION Georg von Alfthan, Helsinki, Finland, assignor toOsakeyhtio Keskuslaboratorio Centrallaboratorium Aktiebolag, acorporation of Finland Filed Apr. 6, 1965, Ser. No. 446,063 Claims. (Cl.73-61) ABSTRACT OF THE DISCLOSURE A known amount of the fibersuspension, such as wood fibers suspended in water, is fed through aslit having a predetermined size such that shives or fiber bundles abovea predetermined maximum size are caught by the slit, whereby to decreasethe rate of liquid flow through the slit. The decrease in flow throughthe slit, which is a measure of the shive or fiber bundle content, isdetermined. A preferred manner of making such determination is to rinsethe slit as soon as it has been clogged to a predetermined extent, andregistering the number of rinsings of the slit for a known amount ofsuspension; the result gives a measure of the content of shives or fiberbundles in the suspension.

It is of great importance that the shives content in a fiber suspensionintended for paper manufacture is as low as possible. Thus it isimportant to check the shives con tent by means of suitable methods ofdetermination. The methods used up to now are rather tedious andtimeconsuming. No method is known for continuous determination of theshives content. The object of the present invention is therefore toeffect a means for rapid determination of the content of shives or fiberbundles with a minimum amount of work.

The main characteristics of the means according to this invention arethat a known amount of the suspension is fed through a slit which, atleast to its main features, consists of two oblique walls, preferablyforming an acute angle, the dimensions of the slit being such thatshives or fiber bundles above a certain maximum size are caught by theslit diminishing the rate of liquid flow, and that the decrease in flowthrough the slit is determined as a measure of the content of shives orfiber bundles.

A suitable way of determination is to rinse the slit as soon as apredetermined extent of clogging has been reached, and the number ofrinsings per the known amount of suspension is registered as a measureof the content of shives or fiber bundles. According to one of themodifications of the invention, a fiber suspension of givenconcentration is fed continuously through the slit, and the rinsingfrequency is recorded as a measure of the content of shives or fiberbundles.

The invention also includes an apparatus for application of the meansdescribed, the apparatus being characterized by a number of devices forthe purpose of feeding a known amount of suspension through a slitwhich, at least to its main features, consists of two oblique walls,preferably forming an acute angle, the dimensions of the slit being suchthat shives or fiber bundles above a certain maximum size are caught bythe slit, diminislring the rate of liquid flow, and by devices forregistration of the decrease in flow through the slit.

The invention is described in more detail in the following withreference to the annexed drawing schematically showing an embodiment ofan apparatus for the determination of the content of shives or fiberbundles in a fiber suspension.

3,359,786 Patented Dec. 26, 1967 In the drawing 1 designates a pulp tankfrom which a pipe 2 provided with a valve 3 leads to an overflow tank 4which is provided with a water inlet having a valve 5. A pipe 6 leadsfrom the overflow tank 4 to the upper portion of a glass tube 7. Theglass tube 7 is provided with a conically widening lower portion 8 theinside of which is ground. Inside the conical portion 8 there isprovided a body 9 concentric with the conical portion 8. In theembodiment shown the body 9 is formed as a spherical segment. Betweenthe body 9 and the conical portion 8 there is formed a narrow slit 10which is dimensioned such that a diluted pulp suspension may flowunimpededly past the body 9 while larger particles, for instance shives,are caught by the slit. The tube 7 is freely suspended from an adjustingknob 11 by means of which the height position of the tube can beadjusted in relation to the body 9 for regulating the Width of the slit10. The adjusting knob 11 is preferably provided with a pointer 12 whichtogether with a corresponding scale 26 directly indicates the width ofthe slit 10. The usable range of the slit is for example between 0.15and 0.60

The spherical body 9 is supported by a pneumatic cylinder 13 which isconnected by a pipe 14 provided with an air valve 15 and a pressurereducing valve 16 to a pressure air source (not shown). A branch line 17leads from the pipe 14 to the pulp tank 1. The air valve 15 is a two-wayvalve having three ports. In the first of its two positions the valve 15connects the source of compressed air to cylinder 13 through two of itsports which are then in communication, the third port, which isconnected to the atmosphere, then being closed. In the second of its twopositions the valve 15 closes the port thereof which is connected to thesource of compressed air, and connects the cylinder 13 to theatmosphere.

In the upper portion of tube 7, above the mouth of pipe 6, there isprovided a contact 18 forming part of an electrical circuit 19. Thecircuit 19 also includes a relay 20 commanding an operating device 21 ofthe valve 15 and a pulse counter device 22. The circuit 19 may furtherinclude a recorder 23 and an alarm device 24 both connected to thecounter device 22.

Below the tube 7 a vessel 25 is provided for the collecting and removalof pulp suspension flowing through the slit 10.

The operation of the apparatus shown is as follows:

The width of the slit 10 is adjusted to the desired value by turning theadjustment knob 11. The height of the overflow tank ,4 above the tube 7is adjusted so that the water level in the tube 7 is in equilibrium at alevel mark at the upper end of the tube. A sample of pulp, for example20 g., is transferred to the pulp tank 1 and diluted to a desiredconcentration. The pulp is kept moving by means of a stream of airthrough the branch line 17. The valve 15 is in its first position, sothat cylinder 13 is held in elevated position by compressed air suppliedto it by pipe 14. The pulp valve 3 is opened, and the pulp flows throughthe pipe 2 to the overflow tank 4 where it meets a stream of water andis further diluted. The pulp is flowing in this diluted condition to thetube 7. The diluted pulp suspension flows unimpededly past the sphericalbody 9 through the slit 10. If the pulp, however, contains particles,such as shives, that are thicker than the width of the slit 10, theseare caught by the slit. As a atmosphere. The air will then leave thecylinder 13 supporting the spherical body 9, and the body 9 falls downso that the slit 10 is widened. All the shives caught by the slit 10 arethen rinsed away by the flow of suspension through the slit 10. Therinsing time is, by adjustment of the air pressure by means of thepressure reducing valve 16, regulated in such a way that the liquidlevel sinks back to the initial equilibrium level. Upon actuation, therelay 20 also gives a pulse to the counter 22. The described procedureis repeated until the entire pulp quantity has flowed through theapparatus. The number of rinsings indicated by the counter 22 serves asa measure of the shive content of the pulp.

Instead of the batchwise operation described above, the apparatus mayalso be run continuously. In that case a pulp suspension having a knownconcentration is continuously fed through the tube 7 and slit 10, theoperation being otherwise as above. The number of rinsings per aselected time unit is recorded by the recorder 23 and serves as ameasure of the shive content of the pulp. The alarm device 24 isarranged to operate when a certain allowable shive content is exceeded.

The invention is not restricted to the embodiment shown and described,which is intended for purposes of illustration only. Thus for example,the tube 7 may as well be arranged to rise for rising of the slit 10,the body 9 being stationary. The shape of the body 9 may also differfrom that shown in the drawing. Further, it is also possible to use alinear slit which then is defined between two plane walls arranged at anangle with respect to each other, one of said walls being adjustable forrinsing of the slit and regulating the width thereof.

I claim:

1. A method for the determination of the shive content of pulps,comprising forming a liquid suspension of a selected amount of pulp,causing said suspension to flow along a restricted path including aslit, dimensioning said slit to allow fibers to pass but to retainparticles exceeding a pre-selected size, detecting a pre-selecteddecrease of flow through said slit caused by its partial clogging byretained particles, momentarily widening said slit for rinsing it ofsaid retained particles upon detecting said decrease of flow, andregistering the number of rinsings per said amount of pulp as 'a measureof the shive content of said pulp.

2. A method for the determination of the shive content of pulps,comprising causing a liquid suspension of pulp to flow continuously at aselected rate of flow along a restricted path including a slit,dimensioning said slit to allow fibers to pass but to retain particlesexceeding a pre-selected size, detecting a pre-selected decrease of flowthrough said slit caused by its partial clogging by retained particles,momentarily widening said slit for rinsing it of said retained particleseach time said decrease of flow has been detected, and registering thenumber of rinsings per time unit as a measure of the shive content ofsaid pulp.

3. An apparatus for the determination of the shive content of pulps,comprising means providing a restricted path including a slit having alength dimension considerably exceeding its width dimension, said slitbeing dimensioned to allow fibers to pass but to retain particlesexceeding a preselected size, means for passing a liquid suspension ofpulp at a selected rate of flow along said path through said slit, meansfor momentarily widening said slit, means responsive to a pre-selecteddecrease of flow through said slit caused by retained particles andcontrolling said means for the widening of said slit, and registeringmeans responsive to said flow responsive means.

4. An apparatus as in claim 3, said restricted path comprising avertical tube having a. conically widening lower portion and a bodyinserted in said lower position concentrically therewith, said tube andsaid body defining together an annular slit.

5. An apparatus as in claim 4, the portion of said body facing thedirection of fiow through said tube being spherical.

6. An apparatus for the determination of the shive content of pulps,comprising a vertical tube having a conically widening lower portion, abody in and concentric with said lower portion, said body and said lowerportion forming together an annular slit having such a width that pulpfibers may pass while larger particles are retained by the slit, meansfor feeding a liquid suspension of pulp in a downward direction throughsaid tube and said slit at such a rate that the suspension flow in saidtube will attain an equilibrium level at a substantial height above saidslit, means for momentarily displacing said tube and said body withrespect to each other in a slit widening direction, an electricalcircuit including circuit closing means located in said tube at aselected height above said equilibrium level and responsive to a risingof the liquid level in said tube caused "by particles retained in saidslit, relay means responsive to said circuit closing means andcontrolling said tube and body displacing means, and pulse counter meansresponsive to said relay means.

7. An apparatus as in claim 6, said tube and body displacing meanscomprising a pneumatic cylinder supporting said body and slidablebetween an upper slit forming position and a lower slit wideningposition, said cylinder being connected to a pressure air source througha valve, said valve being controlled by said relay means.

8. An apparatus as in claim 7, said valve being regulated to retain saidbody in a slit widening position for a period of time sufiicient toallow the liquid level in said tube to return to said equilibriumposition.

9. An apparatus as in claim 8, the portion of said body facing thedirection of flow through said tube being spherical.

10. An apparatus as in claim 9, said electrical circuit furtherincluding recording means and alarm means actuated by said pulse countermeans.

References Cited UNITED STATES PATENTS 2,346,746 4/ 1944 Green 73-633,222,916 12/ 196-5 Davis. 3,276,248 10/1966 Cyr 736l DAVID SCHONBERG,Primary Examiner,

1. A METHOD FOR THE DETERMINATION OF THE SHIVE CONTENT OF PULPS,COMPRISING FORMING A LIQUID SUSPENSION OF A SELECTED AMOUNT OF PULP,CAUSING SAID SUSPENSION TO FLOW ALONG A RESTRICTED PATH INCLUDING ASLIT, DIMENSIONING SAID SLIT TO ALLOW FIBERS TO PASS BUT TO RETAINPATICLES EXCEEDING A PRE-SELECTED SIZE, DETECTING A PRE-SELECTEDDECREASE OF FLOW THROUGH SAID SLIT CAUSED BY ITS PARTIAL CLOGGING BYRETAINED PARTICLES, MOMENTARILY WIDENING SAID SLIT FOR RINSING IT OFSAID RETAINED PARTICLES UPON DETECTING SAID DECREASE OF FLOW, ANDREGISTERING THE NUMBER OF RINSINGS